Spark plugs can be used to initiate combustion in internal combustion engines. Spark plugs typically ignite a gas, such as an air/fuel mixture, in an engine cylinder or combustion chamber by producing a spark across a spark gap defined between two or more electrodes. Ignition of the gas by the spark causes a combustion reaction in the engine cylinder that is responsible for the power stroke of the engine. The high temperature gradients, high electrical voltages, rapid repetition of combustion reactions, and the presence of corrosive materials in the combustion gases can create a harsh environment in which the spark plug must function. This harsh environment can contribute to erosion and corrosion of the electrodes that can negatively affect the performance of the spark plug over time, potentially leading to a misfire or some other undesirable condition.
To help control or reduce the operating temperature of the spark plug electrodes, the electrodes may include a core made of a material having a high thermal conductivity, such as copper (Cu), to help conduct heat away from a sparking end of the spark plug electrodes. The copper core may be surrounded or covered by a cladding or sheath of a material having corrosion and erosion resistant properties, such as nickel (Ni). However, traditional copper cored electrodes can sometimes experience relaxation and/or swelling issues when used in engines running periodically between full throttle and idle operation. In such operation, the electrodes experience significant temperature gradients, which in turn can create thermal stresses that can result in electrode creep, changes to the spark gap, as well as other unwanted consequences.